Thursday, March 3, 2011

Back at the beginning of the year I saw an article in OregonLive about fears of a chromite operation slated to begin near Coos Bay. Much of it was allegations and refutations of potential contamination by hexavalent chromium (the "bad" kind, as opposed to trivalent chromium, the "harmless" kind). I'm not an environmental chemist, so I can't say whether these allegations are valid or not, but I can point out that the chromite is already there in unconsolidated sands. I'm not sure how removing it will change its chemical behavior for the worse- not saying it won't or couldn't, just saying I'm not sure how. A photo caption from The Coos Bay World claims zircon and garnet will be extracted as well.

I saw a talk at OSU during the mid-late 80's, toward the end of my degree, on the potential for offshore mining operations in wave- and current-sorted sands, as well as some onshore prospects in uplifted terrace deposits of the same nature. I don't remember if the Coos Bay prospect was one mentioned, but I do know there were a few on the southern coast, and that chromite was the primary mineral of interest at these sites. (There was also some interest at the time in a titanium mineral- ilmenite, I think- in some areas of the northern coast.) I don't know whether minerals sorted and concentrated by marine shore processes are properly referred to as placers, or if that word specifically implies stream deposits, but the result is the same: heavy minerals become concentrated in certain areas where the competence of flowing water drops off.

The Coos Bay to Bandon stretch of the Oregon Coast is a particularly exciting one, being the transition zone from the Coast Range sedimentary sequence to the Klamath Mountain terranes. A local equivalent to the Franciscan Melange crops out at Bandon, and I have talked about the blueschist I associate with that town here.(In the Google Earth image above, I have copied and moved the scale bar so I could crop out much of the ocean.) That ragged bit of shoreline to the SW of the location named Barview is the site of my three favorite parks on the Oregon Coast: Sunset Bay, Shore Acres and Cape Arago. I'm not going to go into their geology in any detail here, but they sit upon folded and faulted Eocene Coaledo Formation, of Coast range affinity. The blueschist at Bandon is reported to have a Jurassic to Cretaceous age. I don't know if the contact between these two provinces is exposed anywhere; I've never seen it, though I'd love to.

Along with a wide variety of other rocks, one of the notable components of the Klamath Mountains are several ophiolite sequences (the serpentine I posted on a couple of years ago came from the Josephine Ophiolite, which extends from northern California northward quite a way into Oregon) and their associated ultramafic rocks. A common accessory mineral in these rocks is chromite- which in some cases can actually form a fairly large portion of the rock by volume. There are some nice layered chromite/gabbro outcrops at Strawberry Mountain in central Oregon. But in the Klamaths, chromite can be concentrated as stream placers- there were some small, scattered operations in the region during WWII- or as in the case near Coos Bay, concentrated by shore processes.

It may seem like a lot of fuss, but the reason that this is important is that as far as I've been able to tell, the US has no chromium mines at this point, and it is an important metal, both industrially and strategically. Unlike some of the resources I pointed out yesterday, I don't have the sense that we're "running out." The primary world producer is South Africa, followed by India and Kazakhstan. Canada is not listed at that link, but according to an article at Cleveland.com a month ago, that may be about to change. However, for a metal as critical to industry and defense as chromium, to have no domestic source is not a desirable state of affairs. I suspect, given the size of the area under discussion, that the actual production rate will be a mere drop in the bucket compared to total US demand, but it's better than nothing.

The Coos Bay area- much of the Oregon Coast, really- has been under severe economic pressure basically since I moved out here. The decline of the timber industry and restrictions on fisheries to prevent overfishing, combined with high property values, have made life difficult for many coastal workers. While this mine will not profoundly impact US industry, I hope it offers a decent living for a few of my fellow Oregonians. Speaking of which, they're looking for workers.

I think you're right about there being no active chromite mines in at least the lower 49 states. My recollection is that chromite was last mined at the Stillwater Intrusion in Montana during the Korean War. I don't know where else it would've been mined domestically since then.

I grew up there and Sunset beach was a favorite but Shore Acres has a beautiful secluded beach to go with the Botanical gardens.That is where I want my ashes scattered.There was actually a Boardwalk/carnival at Sunset back in the thirties.

On top of the Chromite, I do believe there are old nickel mines in the South Coos Bay area and there are also Coal mines, long abandoned.

BTW, after reading this, I am reminded of my Grand father who use to pan for Gold at Whiskey Run beach and also had a claim between Myrtle Point and Roseburg back in the hills called China Flats.Quite the self educated rock hound, he never graduated High School but one ingenious guy. He worked at Weyerhauser in North Bend as a Millwright for twenty five years and built houses from scratch in his spare time too. He once saw a picture of a portable sluice with a lawnmower engine to shake it back and forth, fed by a pump and nozzle used to root around in the creek beds and built an exact replica from memory.

@Bustedknuckles, Thanks! Each of those three parks seems to have its own personality, and I think that's part of why I like them so much. And those pocket cove beaches- I think I know exactly which one you're talking about at Shore Acres, at the south end of the park?- are wonderful.

There was a nickle mine at Riddle that closed about 1990, but I haven't heard of one near Coos Bay. It's possible, though. There's an iron-nickle mineral alloy called josephinite that also comes out of the ultramafic rocks and gets concentrated as in placer deposits. Gold Beach got its name from gold concentrated in the beach sands there after washing down the Rogue River.